Made the ParserIntItem's scan return DeckItem, and put a virtual scan in ParserItem. The ParserRecord now has a simple, but functioning parse method

opm/parser/eclipse/Parser/ParserItem.cpp

@@ -30,7 +30,7 @@ namespace Opm {
         return m_name;
     }
 
-    ParserItemSizeEnum ParserItem::sizeType() {
+    ParserItemSizeEnum ParserItem::sizeType() const {
         return m_sizeType;
     }